There has been no federally sponsored research or development in this application.
Not applicable
In many industrial operations a liquid slurry or solution of a product is used during its preparation. Then it is a common practice to remove the liquid, most often water, and ship only dry product to the customer. The customer may then use the product in its dry form, or he may reconstitute it with a suitable liquid. Common products so handled are instant coffee and powdered milk.
FIG. 1 shows a typical spray dryer system used industrially to remove liquid from a slurry or solution.
Feed stream 1 is a liquid carrying suspended or dissolved solids which is pumped on to a spinning disk 17 driven at high speed by a motor 3. This action of disk 17 results in atomization of stream 1 into fine droplets 18 within the body of a spray chamber 5. Although a spinning disk is the most common atomizer, other devices include a spray nozzle, two phase spray nozzles and high frequency devices.
A hot-arid drying-gas 2 is introduced through a manifold 4 which directs gas 2 downward into spray chamber 5 where it forms the surrounding atmosphere for droplets 18. As droplets 18 fall through drying gas 2 their liquid component is evaporated which leaves dry particles of product. Most of the dry product passes out of spray chamber 5 at a lower solids discharge 7. Fine particles of product are carried with the drying gas and water vapor through a gas outlet 6 to a cyclone separator 9.
Most remaining solids leave cyclone 9 at a cyclone solids outlet 16 where they join the bulk of collected solids from discharge 7 to form a solids product 12 passing to a final separator 10. Drying gas and water vapor 15 leaving cyclone 9 and carrying very few solids joins vent gas 11 from final separator 10. Both streams pass through a final scrubber or bag filter 14 before venting to a suitable release point 13. Solids leave separator 10 at an outlet 8.
Although FIG. 1 represents a general spray dryer design, there are many variations depending upon the material being processed and the desired product.
The spray dryer design shown by FIG. 1 is highly adaptable to many materials, and it is used widely in many industrial applications. However much of its cost lies in the large spray chamber which may also require a major investment in building space in addition to the spray chamber itself. Also the spray disk and its drive are expensive precision devices, since they often reach speeds in the range of 14,000 rpm. Electrical energy to power the disk is a continuing operating cost.
This invention improves spray-drying equipment by simplifying it which results in savings in investment and in electrical operating cost. A contact zone in the duct used to convey hot gas 2 to manifold 4 and duct 2 itself are used to replace Spray chamber 5 in FIG. 1. A reversed jet nozzle valve described by U.S. Pat. No. 6,419,210 B1 and application Ser. No. 09/690,861 is used to replace spray disk 17 and its electric motor drive 3.
Heating equipment to supply hot-arid air to the dryer including its blower is essentially the same as for a conventional spray dryer. Also, the collection system is similar to that used by conventional spray dryers of the type that includes fluidized bed drying/stripping of residual moisture from the solids.